The CDF plug upgrade electromagnetic calorimeter: test beam results

The CDF Plug Upgrade calorimeter, which fully exploits the tile–fiber technique, was tested at the Fermilab meson beamline. The calorimeter was exposed to positron, positively charged pion and positive muon beams with energies in the range of 5–230 GeV. The energy resolution of the electromagnetic calorimeter to the positron beam is consistent with the design value of , where E is the energy in units of GeV and represents sum in quadrature. The non-linearity for positrons is studied in an energy range of 11–181 GeV. It is important to incorporate the response of the preshower detector, the first layer of the electromagnetic calorimeter which is readout separately, into that of the calorimeter to reduce the non-linearity to 1% or less. The energy scale is about 1.46 pC/GeV with HAMAMATSU R4125 operated typically at a gain of 2.5×10⁴. The response non-uniformity over the surface of a tower of the electromagnetic calorimeter is found to be about 2% with 57 GeV positrons. Studies of several detailed detector characteristics are also presented.     

The sat calorimeter of the DELPHI experiment at LEP; results of a module test

The construction of an electromagnetic calorimeter using scintillating plastic fibres and lead plates is described. The calorimeter is part of the Small Angle Tagger (SAT) of the DELPHI experiment at the LEP collider, recording high-energy electrons, positrons and photons. Results from a test of a module of similar construction are presented. The module was found to have a linear energy response when exposed to electrons of 10–70 GeV, with an energy resolution given by σ/E[%] = (1.16² + (11.4/√E[GeV])²)^1/2.     

Performance of the ATLAS electromagnetic calorimeter barrel module 0

The construction and performance of the barrel pre-series module 0 of the future ATLAS electromagnetic calorimeter at the LHC is described. The signal reconstruction and performance of ATLAS-like electronics has been studied. The signal to noise ratio for muons has been found to be 7.11±0.07. An energy resolution of better than (sampling term) has been obtained with electron beams of up to 245 GeV. The uniformity of the response to electrons in an area of Δη×Δφ=1.2×0.075 has been measured to be better than 0.8%.     

Development of a momentum determined electron beam in the 1–45 GeV range

A beam line for electrons with energies in the range of 1–45 GeV, low contamination of hadrons and muons and high intensity up to 10⁶ per accelerator spill at 27 GeV was setup at U70 accelerator in Protvino, Russia. A beam tagging system based on drift chambers with 160 μm resolution was able to measure relative electron beam momentum precisely. The resolution σ_p/p was 0.13% at 45 GeV where multiple scattering is negligible. This test beam setup provided a possibility to study properties of lead tungstate crystals (PbWO₄) for the BTeV experiment at Fermilab.     

Magneto-transport in porous silicon

Magnetoresistance (MR) measurements have been performed in the temperature range 100–300 K on macroporous porous silicon (P.S.) samples. P.S. layers have been prepared by the anodic dissolution of Si in HF acid. The MR has been found to be positive in P.S. for the temperature range 100–300 K and for the entire range of magnetic field (0–5 kG). However the magnitude of the positive MR is found to be much less than expected on the basis of free electron conduction. Also the value of n in the relation Δρ/ρ_o∞Bⁿ for the temperature range 100–300 K is found to be < 2, implying that there is a contribution of some phenomenon other than the free electron conduction to MR. The measured data suggest that it is the contribution of localized state conduction near the Fermi level and in the localized states near the band edges.     

A 5 in. Si(Li)/Pb sampling calorimeter telescope for observation of cosmic gamma rays in the GeV region

A 5 in. diameter Si(Li)/Pb sampling calorimeter with a depth of 28 radiation lengths (30 unit cells × 0.93 radiation lengths) has been constructed. The energy and angular resolutions of the calorimeter have been investigated using CERN SPS positron beams with energies of 10 to 147.8 GeV. The calorimeter shows good linearity over this energy region and the energy resolution is expressed well by σ_E (rms)/E = (16.9 ± 0.9)%/ √E[GeV], where E represents the incident beam energy. The angular resolution of the calorimeter for a single event is 0.3° (rms) at 80 GeV/c. The agreement between these results and Monte Carlo simulations is good.

We are showing a new design of the Si(Li)/Pb sampling calorimeter telescope (SSCT) with an angular resolution (point source localization capability) of about 0.04° (rms) for bright galactic gamma-ray sources. We believe that this telescope is a suitable detector for future observations of cosmic gamma rays in the GeV region, especially when used to search for point sources.     

Gamma double prime precipitation kinetic in Alloy 718

Gamma double prime (γ′′), precipitation was studied in Alloy 718 using isothermal and isochronal aging heat treatments applied between 943 and 1003 K. It is shown, that the coarsening behavior of γ′′ precipitates follows the coarsening kinetic predictions of the Lifshitz–Slyozov–Wagner (LSW) theory. The activation energy for γ′′ growth has been determined as equal to 272 kJ mol⁻¹ and seems to be controlled by volume diffusion of niobium in the matrix. The energy of the γ′′/matrix interface, Γ, has been found to be 95 ± 17 mJ m⁻² by assuming that the γ′′ precipitates adopt a disk shape which minimizes the total energy. This energy includes a volume distortion term calculated from the Eshelby inclusion theory and a surface component which is assumed to be isotropic. This interfacial energy is discussed and compared with the energy of γ′/matrix and γ′′/matrix interfaces in other superalloys. The constant K′′ of the LSW law time dependence has been calculated using the value of interfacial energy and the activation energy of γ′′ precipitates coarsening and is found to be in good agreement with our experimental values.     

Performance of a BGO calorimeter with photodiode readout and with photomultiplier readout at energies up to 10 GeV

Bismuth germanate (BGO) calorimeter arrays, consisting of up to 12 elements of 30 × 30 × 200 mm³ have been tested at the CERN PS with pions and electrons of up to 10 GeV/c momentum, and at SIN with pions, electrons and protons up to 450 MeV/c. Both photomultiplier (PM) and photodiode (PD) readouts were used. Accurate calibration in the 100 MeV energy range was achieved with stopping protons, stopping pions and minimum ionizing pions. With 212 MeV electrons and PM readout, a time resolution of the BGO signal of 640 ps fwhm has been measured. The energy resolution for electrons above 1 GeV (PD readout) was found to be roughly constant at σ/E ～ 1%. This is consistent with a negligible intrinsic resolution for BGO at these energies, after taking into account shower leakage and PD noise. For electrons of 92 and 200 MeV, we obtained (PM readout) energy resolutions close to the theoretical limit given by photon statistics and shower leakage. The electron/hadron separation was better than 1:500 over the energy range of 0.5 to 10 GeV, and improved to better than 1:1000 after a simple pattern cut. The energy deposition of the e.m. showers, both laterally and longitudinally (rear leakage), was found to be in agreement at the 0.1% level with Monte Carlo calculations using the SLAC-EGS program.     

Performance of an electromagnetic liquid krypton calorimeter based on a ribbon electrode tower structure

The NA48 collaboration is preparing a new experiment at CERN aiming to study CP violation in the K⁰- system with an accuracy of 2 × 10⁻⁴ in the parameter e(ε′/ε). Decays in two π⁰'s will be recorded by a quasi-homogeneous liquid krypton calorimeter. A liquid krypton calorimeter has been chosen to combine good energy, position and time resolution with precise charge calibration and long-term stability. The prototype calorimeter incorporating the final design of the electrode read-out structure is presented in this paper. An energy resolution of 3.5%/√E with a constant term smaller than 0.5% has been obtained. The time resolution was found to be better than 300 ps above 15 GeV.     

The ZEUS forward plug calorimeter with lead–scintillator plates and WLS fiber readout

A Forward Plug Calorimeter (FPC) for the ZEUS detector at HERA has been built as a shashlik lead–scintillator calorimeter with wave length shifter fiber readout. Before installation it was tested and calibrated using the X5 test beam facility of the SPS accelerator at CERN. Electron, muon and pion beams in the momentum range of 10–100 GeV/c were used. Results of these measurements are presented as well as a calibration monitoring system based on a ⁶⁰Co source.     

Spatial distribution of moderated neutrons along a Pb target irradiated by high-energy protons

High-energy protons in the range of 0.5–7.4 GeV have irradiated an extended Pb target covered with a paraffin moderator. The moderator was used in order to shift the hard Pb spallation neutron spectrum to lower energies and to increase the transmutation efficiency via (n,γ) reactions. Neutron distributions along and inside the paraffin moderator were measured. An analysis of the experimental results was performed based on particle production by high-energy interactions with heavy targets and neutron spectrum shifting by the paraffin. Conclusions about the spallation neutron production in the target and moderation through the paraffin are presented. The study of the total neutron fluence on the moderator surface as a function of the proton beam energy shows that neutron cost is improved up to 1 GeV. For higher proton beam energies it remains constant with a tendency to decline.     

Beam test of the CsI(Tl) calorimeter for the BELLE detector at the KEK-B factory

We studied the performance of a prototype electromagnetic calorimeter for the BELLE detector at the KEK proton synchrotron for an energy range of 0.25–3.5 GeV. The prototype consisted of an array of 6 × 5 CsI(Tl) crystals with 30 cm length (16.2 radiation lengths) and about 6 cm × 6 cm cross section. The scintillation light of each CsI(Tl) crystal was read out by two large-area PIN photodiodes and charge-sensitive preamplifiers attached at the rear face of the crystal. We measured the energy and position resolution for electrons and the e/π separation for two sets of matrix configurations: one corresponded to the center and the other to the edge of the barrel calorimeter. The overall performance measured by the test proves that the prototype calorimeter is satisfactory for the use in the BELLE detector.     

Monte Carlo simulation of a transition radiation detector

This paper employs Monte Carlo simulations of the performance of a transition radiation detector (TRD). The program has been written for the TRD in the ZEUS spectrometer, which separates electrons from hadrons in the momentum range between 1 and 30 GeV/c. Both, total charge method and cluster counting method were simulated taking into account various experimental parameters. In particular, it was found that the cluster counting method relies on a quantitative understanding of the background originating from the production of δ-electrons by charged particles. The results of the Monte Carlo calculations are in agreement with experimental data obtained with prototypes within a systematic uncertainty of 20%. We applied our Monte Carlo program to studies in order to find an optimum layout for the TRD within available space in the ZEUS spectrometer. In this context, the performance of TRD layouts with different geometries and materials has been evaluated comprehensively. The geometry found by optimization promises an improvement on hadron suppression by a factor of about two for both methods compared with present results from test measurements. Applying algorithms for a detailed analysis of the energy and space distributions of the clusters in the TRD, hadrons in the momentum range from 1 to 30 GeV/c can be suppressed to a level of less than 2%. This method of cluster analysing improves the suppression of hadrons by a factor of about two compared to the total charge method.     

Thermodynamic calculation of stacking fault energy in Fe–Mn–Si shape memory alloys

Based on thermodynamic considerations together with measurement of the stacking fault probability (Psf) by X-ray diffraction profile analysis, the stacking fault energy (SFE, γ) of austenite in Fe–Mn–Si shaped memory alloys can be estimated. For instance, the stacking fault energy of an fcc(γ) phase in an Fe–30.3Mn–6.06Si was calculated as 7.8 mJ/m². Compositional dependence of stacking fault energy in these alloys with certain composition range has also been derived as SFE(γ)=180.54+7.923 wt.% Mn–46.38 wt.% Si (J/mol), showing that the stacking fault energy increases with the addition of Mn and decreases with the addition of Si.     

Growth, structure and epitaxy of ultrathin NiO films on Ag(001)

NiO ultrathin films have been grown on Ag(001) by Ni deposition in an O₂ atmosphere. The thickness range 5–50 ML has been investigated. X-ray photoelectron spectroscopy has been used to study the stoichiometric composition and chemical purity of the oxide films. We found completely oxidized stoichiometric NiO films. Their contamination has been found to be limited to the topmost layers. Photoelectron diffraction has given information concerning the local crystal structure of the films. The film atomic geometry has been found to be the same independent of thickness in the 0–50 ML range. The films have the expected (001) rock-salt structure with the same in plane orientation as the Ag(001) substrate. Specular X-ray reflectivity has allowed a very accurate thickness evaluation and has given information on the width of the density gradients at the film–substrate and vacuum–film interfaces, found to be of the order of a few atomic layers.     

Preparation and characterization of chemically deposited PbSnS3 thin films

High-quality and well-reproducible PbSnS₃ thin films have been prepared by a simple and inexpensive chemical-bath deposition method from an aqueous medium, using thioacetamide as a sulphide ion source. X-ray diffraction analysis of the deposited films revealed that the as-deposited films were amorphous, however, an amorphous-to-crystalline phase transition was observed as the result of thermal annealing at 425 K for 1 h. The X-ray structure analysis of the collected powder from the bath annealed at 425 K for 1.5 h revealed an orthorhombic phase.

Analysis of the optical absorption data of crystalline PbSnS₃ films revealed that both direct and indirect optical transitions exist in the photon energy range 1.24–2.48 eV with optical band gaps of 1.68 and 1.42 eV, respectively. However, a forbidden direct optical transition with a band gap value of 1.038 eV dominates at low energy (<1.24 eV). The refractive index changes from 3.38 to 2.16 in the range 500–1300 nm. The high frequency dielectric constant and the carrier concentration to the effective mass ratio calculated from the refractive index analysis were found to be 4.79 and 2.3×10²⁰ cm⁻³, respectively. The temperature dependence of the electrical resistivity of the deposited films follows the semiconductor behaviour with extrinsic and intrinsic conduction. The determined activation energies range are 0.35–0.42 and 0.76–85 eV, respectively.     

Adsorption of reactive dyes from aqueous solutions by fly ash: kinetic and equilibrium studies

Adsorption kinetic and equilibrium studies of three reactive dyes namely, Remazol Brillant Blue (RB), Remazol Red 133 (RR) and Rifacion Yellow HED (RY) from aqueous solutions at various initial dye concentration (100–500 mg/l), pH (2–8), particle size (45–112.5 μm) and temperature (293–323 K) on fly ash (FA) were studied in a batch mode operation. The adsorbent was characterized with using several methods such as SEM, XRD and FTIR. Adsorption of RB reactive dye was found to be pH dependent but both RR and RY reactive dyes were not. The result showed that the amount adsorbed of the reactive dyes increased with increasing initial dye concentration and contact time. Batch kinetic data from experimental investigations on the removal of reactive dyes from aqueous solutions using FA have been well described by external mass transfer and intraparticle diffusion models. It was found that external mass transfer and intraparticle diffusion had rate limiting affects on the removal process. This was attributed to the relatively simple macropore structure of FA particles. The adsorption data fitted well with Langmuir and Freundlich isotherm models. The optimum conditions for removal of the reactive dyes were 100 mg/l initial dye concentration, 0.6 g/100 ml adsorbent dose, temperature of 293 K, 45 μm particle size, pH 6 and agitation speed of 250 rpm, respectively. The values of Langmuir and Freundlich constants were found to increase with increasing temperature in the range 135–180 and 15–34 mg/g for RB, 47–86 and 1.9–3.7 mg/g for RR and 37–61 and 3.0–3.6 mg/g for RY reactive dyes, respectively. Different thermodynamic parameters viz., changes in standard free energy, enthalpy and entropy were evaluated and it was found that the reaction was spontaneous and endothermic in nature.     

Temperature dependence of the band gap, refractive index and single-oscillator parameters of amorphous indium selenide thin films

InSe thin films are obtained by evaporating InSe crystal onto ultrasonically cleaned glass substrates under pressure of 10⁻⁵ Torr. The structural and compositional analysis revealed that these films are of amorphous nature and are atomically composed of 51% In and 49% Se. The reflectance and transmittance of the films are measured at various temperatures (300–450 K) in the incident photon energy range of 1.1–2.1 eV. The direct allowed transitions band gap – calculated at various temperatures – show a linear dependence on temperature. The absolute zero value band gap and the rate of change of the band gap with temperature are found to be (1.62 ± 0.01) eV and −(4.27 ± 0.02) × 10⁻⁴ eV/K, respectively. The room temperature refractive index is estimated from the transmittance spectrum. The later analysis allowed the identification of the static refractive index, static dielectric constant, oscillator strength and oscillator energy.     

Transport property of Sn-doped In0.5Ga0.5P layers grown by liquid phase epitaxy

The temperature-dependent Hall mobility and carrier concentration of Sn-doped In_0.5Ga_0.5P epilayers grown on (100) semi-insulating GaAs substrates by the liquid phase epitaxy technique have been investigated in the range of 77–300 K. It was found that the Sn-doped In_0.5Ga_0.5P epilayer was heavily compensated with the compensation ratio of 0.4–0.6. It was also found that the Sn shallow donor has an ionization energy 17–12 meV with increasing carrier concentrations through Hall measurements. The model taking into account ionized impurity, alloy and space-charge scattering mechanisms is considered in order to properly portray the observed features of the electron mobility results. The theoretical prediction is in good agreement with the observed results. The electron mobility was limited by ionized scattering up to 120 K and was also limited by alloy, space-charge scattering up to 300 K.     

Deposition and modification of titanium dioxide thin films by filtered arc deposition

Thin films of titanium dioxide have been deposited on glass substrates and conducting (100) silicon wafers by filtered arc deposition (FAD). The influence of the depositing Ti⁻ energy, substrate types and substrate temperature on the structure, density, mechanical and optical properties have been investigated. The results of X-ray diffraction (XRD) showed that with increasing substrate bias, the film structure on silicon substrates changes from anatase to amorphous and then to rutile phase without auxiliary heating, the transition to rutile occurring at a depositing particle energy of about 100 eV. However, in the case of the glass substrate, no changes in the structure and optical properties were observed with increasing substrate bias. The optical properties over the range of 300–800 nm were measured using spectroscopic elliosometery, and found to be strongly dependent on the substrate bias, film density and substrate type. The refractive index values of the amorphous, anatase and rutile films on Si were found to be 2.56, 2.62 and 2.72 at a wavelength of 550 nm, respectively. The hardness and elastic modulus of the films were found to be strongly dependent on the film density. Measurements of the mechanical properties and stress also confirmed the structural transitions. The hardness and elastic modulus range of TiO₂ films were found to be between 10–18 and 140–225 GPa, respectively. The compressive stress was found to vary from 0.7 to 2.6 GPa over the substrate bias range studied. The composition of the film was measured to be stoichiometric and no change was observed with increasing substrate bias. The density of the film varied with change in the substrate bias, and the density ranged between 3.62 and 4.09 g/cm³.